Peel onion, chop. Cut beef into medium-sized cubes. Heat the lard in a large pot. Fry the onions, while stirring continuously, over a high heat until they become golden (not brown). The colour of the juice depends on the colour of the fried onions. Add paprika, sauteé for only 3 seconds (the goulash aquires a bitter taste otherwise). Douse with a shot of vinegar and the water. Add the shank. Season with a pinch of salt, crushed garlic cloves, tomato puree and goulash spice. Simmer for two to three hours uncovered. Stir occasionally until the meat is soft but still firm and the goulash has acquired a beautiful red-brown colour. Add water until you have a thick sauce, if there is too little liquid.